FIG. 7 shows a conventional circuit breaker. Reference numeral 1 represents a case made of mold resin, and reference numeral 2 represents a cover made of mold resin. Inside the case 1 are a power supply-side terminal plate 3, a second movable contact 4, a first movable contact 5, an arc-extinguishing chamber 6, a switching mechanism 7, an operating handle 8, an overcurrent tripping device 9, a load-side terminal plate 10, and the like.
The operating handle 8 is a resin-molded article that has a knob portion 8b provided upright at the center of a flange-shaped base portion 8a having an arc-shaped cross section. The base portion 8a is joined to the top portion of a swing-type handle lever 11, and the knob portion 8b, which protrudes outward through a handle window frame 2a opened on a cover 2, is operated manually to the ON or OFF position (see Patent Literature 1, for example).
Incidentally, the size of the base portion 8a that extends in a movable direction of the knob portion 8b can be made larger than the size of the handle window frame 2a in order to prevent the entry of dust into the case 1 through the handle window frame 2a opened in the cover 2. However, in view of the spaces for disposing the other breaker functional components, it is difficult to increase the size of the base portion 8a of the operating handle 8, raising the risk of enlarging the entire circuit breaker.
Based on Patent Literature 2, the applicants of the present invention have contrived a technique for reducing the size of the operating handle 8 by forming a small base portion, in which a sheet-shaped handle shutter, laid between the base portion and the handle window frame and fitted externally to the knob portion, is moved along with the knob portion to close the space between the base portion and the handle window frame.
Patent Literature 1: Japanese Patent No. 3296460
Patent Literature 2: Japanese Patent No. 4253701